title: Isomerization of spirobenzopyrans bearing electron-donating and electron-withdrawing groups in acidic aqueous solutions.
abstract: Spirobenzopyrans, which are well known as photochromic compounds, exist as thermodynamically stable protonated ring-opened isomers (protonated merocyanine form, McH) in an acidic aqueous solution in the dark. In the present study, we investigated effects of substitution of the spirobenzopyrans on a ring-opening behavior in an aqueous system. We prepared five polymerizable spirobenzopyrans that are substituted with a methoxy group or a nitro group at the 6'- or 8'-positions and without a substituent. These monomers were copolymerized with N,N-dimethylacrylamide to evaluate the spirobenzopyrans in aqueous solution. Correlation between ring-opening rates and the kind and position of the substitution can be summarized as follows: the substitution of an electron-donating methoxy group and the substitution at the 8'-position increased the ring-opening rate, whereas the substitution of an electron-withdrawing nitro group decreased the rate. The effects of the substitution can be explained by changes in the electron density of the oxygen atom of the spirobenzopyrans.
authors.affiliation: Research Center for Stem Cell Engineering, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 5, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8568, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Satoh
authors.forename: Kimio
authors.initials: K
authors.lastname: Sumaru
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takagi
authors.forename: Katsuki
authors.initials: K
authors.lastname: Takai
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kanamori
mesh_terms: D000143:Acids / Q000737:chemistry*; D001578:Benzopyrans / Q000138:chemical synthesis / Q000737:chemistry*; D004583:Electrons; D007536:Isomerism; D012996:Solutions / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013141:Spiro Compounds / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000143:Acids; D001578:Benzopyrans; D012996:Solutions; D013141:Spiro Compounds; D014867:Water